Other link functions: Other link functions for binary data include the inverse cdf of a t distribution (the probit being the limit as df → ∞); a log-gamma link (Genter and Farewell 1985), for which probit, complementary log–log and log–log are special cases; a family of link functions that includes the logit (Pregibon 1980); and extensions with shape parameters that modify the logistic curve in extreme probability regions (Aranda-Ordaz 1981; Stukel 1988).